Citrus greening disease, described by one expert as 'a citrus grower's worst nightmare,' is spread by an infestation of the Asian citrus psyllid.

Leaders of California's $1.6-billion citrus industry said Monday that a disease that was killing orchards worldwide was now rooted in Mexico, and experts warned that it was headed toward the state.

Citrus greening disease has infected six citrus trees on Mexico's Yucatan Peninsula, spread by an infestation of the Asian citrus psyllid.

There's a virtual insect highway across the width of Mexico, and once the aphid-like insect hops on, California is in trouble, said Beth Grafton-Cardwell, a UC Riverside entomologist and director of the Lindcove Research and Extension Center, east of Visalia.

Mexico "is infested with the bug and they will gradually move the disease across the country," Grafton-Cardwell said. "This disease is a citrus grower's worst nightmare."

U.S. and Mexican authorities are working together on solutions. In June, officials from the two countries as well as Belize met to discuss the severity of the infestations and ways to wipe to it out. They will meet again next month.
U.S. officials credited homeowners and growers for many of the insect discoveries so far, and urged them to remain alert.
Farmers shared their concern.

"This is an existential threat. It would put us out of business," said Jim Churchill, a Pixie tangerine grower in Ojai.
The disease doesn't affect humans, but it's lethal to citrus trees. It ruins the taste of fruit and juice before killing the plants, experts said, and there is no known way to rid a region of the pathogen once it has struck.

The disease has killed tens of thousands of acres of trees in Florida and threatens to put the Sunshine State out of the orange juice business, according to the state's Department of Citrus.

Since its discovery in Florida in 2005, the disease has quickly spread to every citrus-growing county in the state, contributing to the death of about 5% of its trees every year. It has wiped out much of the citrus industries in China, India, Saudi Arabia and Egypt, and has ravaged parts of Brazil.
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